Neck orienting method of bottles of saturated polyester resins

ABSTRACT

Herein disclosed is a method of orienting the neck of a bottle of a saturated polyester resin so as to enhance the physical properties and durability of the neck. The neck orienting method includes the step of inserting an orienting rod having a taper head into the neck which is being heated. The neck orienting method may include the step of orienting only the mouth edge of the neck.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bottle made of a saturated polyesterresin, and more particularly to a neck orienting method of orienting notonly the trunk but also the neck of the bottle thereby to enhance thephysical properties and durability of the bottle neck.

2. Description of the Prior Art

Saturated polyester resins such as polyethylene terephthalate haverecently been used in various fields because of their excellent physicalproperties and durability. However, these excellent properties are notexhibited until the moldings of such resins are subjected to anorienting treatment.

Therefore, the molding method of the saturated polyester resin bottlesis generally limited to the blow molding method.

The current molding procedures of the saturated polyester resin bottlesinclude the steps of injection-molding a bottomed cylindrical parison asa primary molding, orienting the neck of the parison, while being heldin a blow mold, in the axial direction with the use of an orienting pin,and injecting a fluid under pressure into the oriented parison toblow-mold a bottle having a shape according to a blow mold. As isapparent from those molding procedures, however, the neck of the bottleis completely left unoriented.

As a result, the neck of the bottle exhibits inferior physicalproperties and durability compared to other portions. For instance, ifthe bottle thus molded is filled with alcohol of high concentration,only its neck (which has not been biaxially oriented) is whitened andbecomes mechanically fragile due to attack of the alcohol.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide amethod of easily orienting the neck of a bottle made of a saturatedpolyester resin thereby to enhance the physical properties anddurability of the bottle as a whole.

A second object of the present invention is to provide a method oforienting the neck of the bottle, expecially, the mouth edge of theneck, which is liable to become mechanically fragile, thereby to preventthe same from being deteriorated.

A third object of the present invention is to provide a method of makingit possible to orient the neck of the bottle without fail in accordancewith the design.

A fourth object of the present invention is to provide a method of oncereducing the neck of a parison into a converging taper shape and thenorienting the neck at a high orienting ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will becomeapparent from the following description with reference to theaccompanying drawings, in which:

FIGS. 1 to 3 illustrate a first embodiment of a bottle neck orientingmethod according to the present invention: FIG. 1 is a diagrammaticalview showing the relationship between a parison before its orientingprocess and an orienting rod; FIG. 2 is also a diagrammatical view butshows the relationship between the parison after its orienting processand the orienting rod; and FIG. 3 is also a diagrammatical view showingthe condition under which the parison oriented is being blow-molded.

FIGS. 4 and 5 are a side elevation and a top plan elevation showingmouth holding arms for holding the mouth of the parison without fail sothat they may neither be compressed nor deformed while being orientedaccording to the first embodiment, respectively.

FIGS. 6 and 7 illustrate the cases, in which the neck is formed on itsouter circumference with a thread while being oriented according to thefirst embodiment: FIG. 6 is a longitudinal section showing the conditionbefore the orienting process; and FIG. 7 is also a longitudinal sectionbut shows the condition after the orientation and the formation of thethread.

FIGS. 8 and 9 illustrate the cases, in which the neck is formed inadvance on its outer circumference with the thread when the parison ismolded: FIG. 8 is a longitudinal section but shows the condition beforethe orientation; and FIG. 9 is also a longitudinal section but shows thecondition upon completion of the orientation.

FIG. 10 is a diagrammatical view showing the relationship between theparison and the orienting rod which is modified from the orienting rodof the first embodiment.

FIG. 11 is a diagrammatical view showing the relationship between theparison before the orientation and the orienting rod before theorientation and the orienting rod according to a second embodiment; andFIG. 12 is also a diagrammatical view but shows the relationship betweenthe parison after the orientation and the orienting rod according to thesame embodiment.

FIG. 13 is a diagrammatical view showing the relationship between theparison before the orientation and the orienting rod according to athird embodiment; and FIG. 14 is also a diagrammatical view but showsthe relationship between the parison after the orientation and theorienting rod according to the same embodiment.

FIGS. 15 to 20 illustrate a fourth embodiment of a bottle neck orientingmethod according to the present invention: FIG. 15 is a sectional viewshowing the parison which has been subjected to the injection moldingtreatment; FIG. 16 is also a sectional view but shows the conditionunder which the neck of the parison is reduced; FIG. 17 is also asectional view but shows the condition under which the neck is orientedafter the reducing treatment; FIG. 18 is also a sectional view but showsa bottle which is produced by blow-molding the parison; FIG. 19 is alsoa sectional view but shows the case in which only the mouth edge of theneck of the parison is reduced; and FIG. 20 is also a sectional view butshows the condition under which the mouth edge of the neck shown in FIG.19 is oriented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be described withreference to FIGS. 1 to 3. First of all, a saturated polyester resin isinjection-molded into a generally tubular parison 1. This parison 1 isconstructed to include a bottom 2, a trunk 3 extending upwardly from thebottom 2, a shoulder 4 reduced from the trunk 3, and a neck 5 having asmaller diameter than the trunk 3. The neck 5 is formed at its upperextremity with an outwardly bulging mouth edge 6 and is made slightlythicker than that which will be used, as it is, as the neck of a bottleproduct without being oriented according to the prior art.

Then, the lower portion of the parison 1 is held in a body holder 7 andis arranged in an upright position, as shown in FIG. 1, so that the neck5 may be oriented be means of the orienting rod 8 of an orientingdevice.

The body holder 7 is composed of a pair of holder halves forming acavity corresponding to the parison 1 and is lined with a frictionmember 9 which is to be brought into the parison 1.

On the other hand, the orienting rod 8 is composed of a converging taperhead 8a and a straight rod body 8b which extends from such a portion asthe outer diameter of the taper head 8a restores the inner diameter ofthe neck of the bottle.

Prior to the orientation, the neck 5 is heated to a temperature higherthan such a glass transition level as can orient the neck 5. Thisheating step of the parison 1 is performed by the well known methodusing an altrared ray or hot wind before the parison 1 is held in thebody holder 7. The parison 1 may be heated after it is held inaccordance with the producing procedures adopted.

In order to orient the neck 5, the orienting device is then operated toforce the orienting rod 8 into the neck 5. With a view to smootheningthat insertion, it is desired that the slope of the taper head 8 of theorienting rod 8 be as gentle as possible. It is also desired that theorienting rod 8 be made slidable without any difficulty either byapplying a lubricant to the taper head and/or the rod body 8b or bylocally cooling and solidifying only the inner wall of the neck 5. If,in this way, the rod body 8b of the orienting rod 8 is inserted until itreaches the lower end of the neck 5, this neck 5 is radially expandedand oriented to the last.

After that, the parison 1 having its neck oriented is blow-molded, asshown in FIG. 3, so that they may be biaxially oriented according to theprior art. More specifically, the parison 1 is held in a blow mold, anda fluid under pressure is pumped into the parison 1, while the bottom ofthe parison 1 is being pushed downward by means of an orienting pin P,until the desired bottle product is made.

As has been described hereinabove, according to the bottle neckorienting method of the present invention, the orienting rod is smoothlyforced into the neck of the parison by the action of the taper head ofthe orienting rod so that the working efficiency can be enhanced, whileensuring the desired accurate orientation, in the production of thesaturated polyester resin bottle which is excellent in the physicalproperties and durability.

Although it is described in the above that a lubricant is applied to thetaper head 8a with a view to reducing the frictional resistance betweenthe orienting rod 8 and the neck 5, it is still difficult to completelyeliminate that frictional resistance. As a result, the neck may beslightly constricted and deformed during the inserting operation of theorienting rod 8 into the neck 5.

Therefore, in case it is necessary to completely eliminate theconstriction and deformation at the parison neck 5, this neck is head,as shown in FIGS. 4 and 5, by means of mouth holding arms 10 which aremade movable back and forth. In this case, more specifically, the mouthedge 6 of the neck 5 is retained at its four portions by the leadingends of the respective holding arms 10, and these holding arms 10 aremoved back and fourth through a not-shown cam mechanism or the like inaccordance with the length of insertion of the orienting rod 8 into theneck 5. Since use is made of the fact that the radius of the taper head8a of the orienting rod 8 is varied with the length of insertion of therod, 8, it becomes possible to orient the neck 5 in an accurate size.

Turning now to FIGS. 6 and 7, the description proceeds to the case, inwhich a thread 11 is formed on the outer circumference of the neck 5simultaneously as the neck 5 is oriented with the use of the orientingrod 8. In this case, the neck 5 of the parison 1 held in the body holder7 is positioned in a neck shaping mold 13 which is formed with a femalethread 12 in its inner wall. If the aforementioned orienting rod 8 isforced into the neck 5, as shown in FIG. 7, the desired male thread 11is formed on the outer circumference of the neck 5 simultaneously asthis neck 5 is oriented. The thread 11 thus formed can enjoy a highaccuracy in size because it is unnecessary to orient the neck 5thereafter.

With reference to FIGS. 8 and 9, the description is changed to the case,in which a thread 14 is formed on the outer circumference of the neck 5of the parison 1 upon the injection molding process of the parison 1.

In this case, it is unnecessary to use the mold shown in FIGS. 6 and 7but is sufficient to orient the neck 5 by the forcing action of theorienting rod 8 into the parison 1 which is formed with the thread 14 inadvance. However, when the neck 5 is oriented by the orienting action ofthe orienting rod 8, the thread 14 which has already been formed by thattime is also oriented. It is therefore necessary to make the thread 14slightly thicker, while taking the subsequent orientation intoconsideration, when the thread 14 is to be formed at first by theinjection molding process.

Although the orienting rod used in the foregoing neck orientation iscomposed of one taper head and one rod body, it is desired in the caseof a relatively large expansion that an orienting rod 19 having a stepshape shown in FIG. 10 be used. The orienting rod 19 in this case isconstructed to include not only a taper head 15 and a straight neck 16but also a taper shoulder 17 and a rod body 18. If desired,incidentally, the orienting rod 19 may be shaped to have two or moresteps.

By forming the leading end of the orienting rod 19 into a multi-stepshape, the orienting operation of the neck 5 can be attained without anydifficulty.

Although, in the foregoing description, the parison is made to have itsneck smaller than its trunk, the shape of the parison is not limited tothat and can be extended to that, in which the neck and the trunk havethe same diameter.

A second embodiment of the present invention will now be described withreference to FIGS. 11 and 12. According to the second embodiment, theorienting device is constructed to have its orienting rod 20 connectedto an ultrasonic wave generator 21 so that it may act as an ultrasonicwave generating horn.

The orienting rod 20 is shaped to include a taper head 22 at its leadingend and a neck 23 extending upward from the taper head 22. The neck 23is formed at its upper portion with a step shoulder 24 having such alength as regulates the insertion of the neck 23 into the parison neck5.

When the neck 5 is to be oriented with the use of the orienting devicethus constructed, the orienting rod 20 is forced gradually, whilegenerating the ultrasonic waves, into the parison neck 5 being held.When the orienting rod 20 begins to contact with the inner wall of theneck 5, this neck 5 is heated to such a temperature by the ultrasonicwaves generated from the orienting rod 20 as has the orienting effects.Simultaneously with this, the orienting rod 20 is forced into the neck 5so that this neck 5 is oriented in such a form as to be radiallyexpanded. Since, in this instance, the orienting rod 20 goes into theneck 5 while generating the ultrasonic waves, the frictional resistanceto be established between the orienting rod 20 and the neck 5 is soremarkably reduced that the insertion can be smoothly attained.

After that, the orienting rod 20 is further forced into the neck 5 untilits step shoulder 24 abuts against the uppermost end of the mouth of theparison, thus completing the orientation of the neck.

In these ways, it is sufficient that the orienting rod generating theultrasonic waves is inserted into the neck 5. In case, however, it isintended to finish the orienting operations of the neck 5 within ashortened time period, the whole body or inner wall of the neck shouldbe heated to some extent before it receives the orienting rod 20. Since,in this case, the heat to be generated from the orienting rod by theultrasonic waves may be reduced to a smaller quantity, the insertingspeed of the orienting rod can be accordingly increased.

As is apparent from the foregoing description, according to the secondembodiment, the ultrasonic waves are used as a heat source for orientingthe neck 5 and are generated from the orienting rod 20. As a result, theheating operation of the neck 5 can be performed remarkably efficientlyand effectively. Moreover, the frictional resistance between the neckand the orienting rod can be reduced to such a low level that theorienting process can be accordingly performed while maintainingremarkably high accuracy in orienting sizes.

A third embodiment of the present invention will now be described withreference to FIGS. 13 and 14. In accordance with this third embodiment,only the mouth edge of the parison neck is to be subjected to theorienting treatment. In other words, that portion of the neck, which isthe most liable to lose the durability, is oriented.

The neck 26 of a parison 25 to be used in the third embodiment is formedduring the injection molding process with a mouth edge 27 which isstepwise reduced and which is located at the uppermost end of the neck26.

In order to orient the mouth edge 27 of the parison 25, this parison 25is held at its neck 26 by means of a neck holder 28. This neck holder 28is constructed to have its upper side positioned at the same level asthe lower end of the mouth edge 27 and is composed of two groovedsemicircular halves, which are brought into abutment engagement witheach other thereby to hold the neck 26. A mold 29 is overlaid on theupper side of the neck holder 28. The mold 29 is formed at its centerwith a hole, which encloses the mouth edge 27 of the neck 26 at aspacing therefrom, and with an annular stopper projection 30 which islocated at the lower inner wall edge of the hole to provide a stopper.

The neck 26 is held in the manner thus far described, and the the mouthedge is heated to the orientable temperature. Then, an orienting rod 31is forced into the mouth edge 27. The orienting rod 31 to be used in thethird embodiment is constructed to include a shorter taper head 32 and ashorter straight neck 33 than the taper rod and the rod body of thefirst embodiment. This is because only the mouth edge 27 is orientedaccording to the third embodiment. On the other hand, the orienting rod31 is formed with such a step 34 at the upper end of the straight neck33 as provides a stopper to regulate the insertion length of theorienting rod 31.

As is seen from FIG. 14, therefore, when the orienting rod 31 isinserted into the mouth edge 27, this edge 27 is forced into the annularclearance between the orienting rod 31 and the mold 29 so that the mouthedge 27 is molded and oriented.

According to the third embodiment thus far described. the mouth edge ofthe neck 26 can be located oriented so that it can exhibit the desiredexcellent physical properties and durability. As a result, the sealingeffects and mechanical strength at the plug portion of the saturatedpolyester resin bottle produced according to the third embodiment can beprevented from being deteriorated. Even in case, moreover, the bottleneck is formed on its outer circumference with the thread, that portionis not subjected to the orienting treatment so that the accuracy of thethread can be maintained excellent. Incidentally, although theorientation of the mouth edge is performed prior to the blow moldingtreatment of the bottle trunk, it may be accomplsihed after the blowmolding treatment, if desired.

Finally, a fourth embodiment of the present invention will now bedescribed with reference to FIGS. 15 to 20. According to this fourthembodiment, the parison neck is once pressed into a converging shape andthen is oriented with the use of an orienting rod so that its mouth edgemay be subjected to the highest orienting treatment.

More specifically, a parison 35 having its trunk and neck of the samediameter, as shown in FIG. 15, is prepared by the injection moldingprocess and is held at its trunk by means of a parison holder 36. Then,the neck 37 of the parison 35 is heated to about 100° C., and a reducingmold 39 having a taper inner wall 38 is pressed onto the neck 37 so thatthis neck 37 is reduced into a taper shape, as shown in FIG. 16.

After that, the neck 37 is further heated to the orientable temperature,and the parison 35 is held in a shaping mold 40. Then, the orienting rod41 of an orienting device is forced into the parison 35 thus prepared,as shown in FIG. 17. The orienting rod 14 being used is made similar tothat of the first embodiment such that it is formed at its leading endwith a curved taper head 42.

After that, the parison 35 thus prepared is subjected to the normal blowmolding treatment so that the bottle shown in FIG. 18 is produced.

If, on the other hand, it is intended to orient only the mouth edge 43of the neck, only this mouth edge 43 may be pressed into a taper shape,as shown in FIG. 19, and then be oriented, as shown in FIG. 20.

The orienting device 44 shown in FIG. 20 is constructed to include aplunger 46 carring a lower piston 45 at its leading end, an elastictubular member 47 mounted on the plunger 46, and an upper piston 48connected to the upper end of the plunger 46 while sandwitching thetubular member 47 between itself and the lower piston 45. Acommunication passage 49 is formed in the upper piston 48 and theplunger 46 so that air under high pressure is injected therethrough ontothe inner wall of the elastic tubular member 47 to expand the upperportion of the tubular member 47. As a result, the neck 43 is forcedonto a shaping mold 50 so that it is oriented.

As has been described hereinabove, according to the fourth embodiment,in case the parison neck is once pressed and then is oriented, theparison can be molded to have its neck and trunk of the same diameter sothat its molding process can be simplified. Since, moreover, the parisonneck is oriented into a cylindrical shape after it has been pressuedinto the taper shape, its mouth edge, which might otherwise beexpecially liable to be cracked, can be oriented to the most extent,which is desired from the standpoint of the orienting treatment.

What is claimed is:
 1. A method of forming the neck portion of asynthetic resin bottle, the method comprising the steps of:(a) forming aparison of synthetic resin, the parison having a neck portion and anoutwardly projecting lip at the upper outer circumferential end of theneck portion; (b) heating the neck portion of the parison to anorientable temperature; (c) holding the parison so that the outwardlyprojecting lip is retained by a plurality of radially extending arms,said arms being movable back and forth on a horizontal plane; (d)inserting an orienting rod into the neck portion of the parison, theorienting rod having a converging tapered head and a straight bodyportion, the straight body portion being of a diameter greater than thediameter of the neck portion prior to insertion of the orienting rod,the neck portion being radially stretched thereby; and (e) moving thearms radially outwardly as the tapered portion of the orienting rod isinserted into the neck portion of the parison whereby said arms continueto hold the parison as the neck portion thereof is radially stretched.2. The method according to claim 1, wherein the step of moving the armsradially outwardly is performed in accordance with the length ofinsertion of the tapered head of the orienting rod into the neck portionof the parison.
 3. The method according to claim 2, wherein said parisonincluding the neck portion and lip thereof is formed by injectionmolding the synthetic resin.
 4. The method according to claim 3, whereinthe portion of said parison other than said neck portion is biaxiallyoriented to form the synthetic resin bottle.
 5. A method as set forth inclaim 1, wherein a thread is formed on the neck of said parison duringthe injection molding process of said parison.
 6. A method as set forthin claim 1, wherein said orienting rod is formed with a plurality ofstepped, tapered heads.
 7. A method as set forth in claim 1, whereinsaid orienting rod is formed at its base with a step shoulder acting asa stopper to regulate the length of insertion thereof into the neck ofsaid parison.
 8. A method as set forth in claim 1, wherein saidorienting rod is connected to an ultrasonic wave generator so that itmay be inserted while generating ultrasonic waves therefrom.